1. Field of the Invention
The present invention relates to: a moving picture data playback apparatus and a moving picture data playback method, in which special playback, such as high-speed playback, of moving pictures is carried out; a moving picture data recording apparatus and a moving picture data recording method for recording the moving picture data played back by the moving picture data playback apparatus; and a recording medium having the moving picture data recorded thereon.
2. Description of the Related Art
In a moving picture data playback apparatus for playing back moving pictures, fast-forward/fast-reverse playback (high-speed playback) of pictures is carried out to retrieve desired scenes.
A conventional moving picture data playback apparatus selectively reads and plays back only intraframe-coded frame pictures (i.e., intra pictures) in moving picture data recorded on a recording medium such as an optical disk, so as to achieve high-speed playback of the moving pictures (see Japanese Laid-Open Publication No. 2762765, for example).
Another conventional playback apparatus generates, in advance, moving picture data for high-speed playback, which has a smaller number of pixels than moving picture data for normal-speed playback, and then records the moving picture data for high-speed playback on a recording medium. By reading and playing back the recorded data, the playback apparatus achieves high-speed playback (see Japanese Laid-Open Publication No. 6-339113, for example).
In helical scan VTRs, the tracks on a tape are accessed across the tracks at a speed higher than a normal playback speed, and slices in which all of the blocks contained are intra-frame coded are decoded one by one. The decoded slices are superimposed on the already displayed picture, whereby high-speed playback is performed (see Japanese Laid-Open Publication No. 3056653, for example)
However, in the configuration in which intra pictures are selectively read from an optical disk to achieve high-speed playback of the moving pictures, the access speed to the optical disk is not sufficiently high, depending upon the playback speed. As a result, all of the intra pictures cannot be read in time for the display. Therefore, when the intra pictures are read, some of them have to be skipped, which leads to a problem in that the high-speed playback cannot be performed smoothly and some of the short scenes cannot be retrieved.
In the configuration in which moving picture data for high-speed playback is generated and recorded in advance, if the generated moving picture data for high-speed playback is played back as it is, no problem will occur. However, in a case in which the playback speed is changed and the moving picture data for high-speed playback is played back at a higher speed, the moving picture data for high-speed playback has to be read with some part thereof being skipped, which leads to the problem that smooth high-speed playback cannot be performed, as in the example in which the intra pictures are selectively read from the optical disk for the high-speed playback of the moving pictures.
Also, in the case of a recording medium, such as an optical disk, that has a spiral or concentric track structure, it is difficult to read the data on the recording medium across the track or the tracks. It is thus difficult to apply the example of high-speed playback achieved in the VTR to a moving picture data playback apparatus for playing back a recording medium having a track structure.